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Specification

Runtime System

  • PencilBox is a stack based VM.
variables description
env the object share with the outside of VM
ctx the context of canvas in HTML
pc program counter(pointer to the current byte)
stack store and calcuate temp values
stack_scopeindex the list of the index of the start of current stack length when a new scope generated
varstack store values for local variable definition
varstack_callindex the list of the index of the start of arguments in var_stack of current calling function
textstack store all the texts defined in program
funcstack store JIT compiled functions

JIT Compiler

  • PencilBox will convert any func to native JavaScript funciton.

Bytecode Definition

EOT

The unicode for end of text 0x0300

Tips

  • 0xHH means one byte with any content
  • 0xHHHH[] means a list with multiple of two bytes

Opdata

  • The constructor of data types
  • The runtime system will push all the value in Opdata construction to stack
operation name code description construction
sot 0 the start of text(represented as utf-16) sot 0xHHHH[] EOT
iot 1 the index of textstack iot Opdata
int8 2 signed 8-bit integer int8 0xHH
uint8 3 unsigned 8-bit integer uint8 0xHH
int16 4 signed 16-bit integer int16 0xHHHH
uint16 5 unsigned 16-bit integer uint16 0xHHHH
int32 6 signed 32-bit integer int32 0xHHHHHHHH
uint32 7 unsigned 32-bit integer uint32 0xHHHHHHHH
float32 8 32-bit float float32 0xHHHHHHHH
float64 9 64-bit float float64 0xHHHHHHHH 0xHHHHHHHH

Opimplicit

  • The operations generated by compiler
operation name code description construction
textstack 16 the mark of text stack textstack 0xHHHHHHHH (0xHHHH[] EOT)[]
sweep 17 pop the top element from variable stack sweep
sweepn 18 pop n top elements from variable stack sweep 0xHH
jump 19 pop the top element from stack and jump to the specific value of pc jump
jumpoffset 20 pop the top element from stack and jump to the value offset to the current pc jumpoffset
localfget 21 push the the content in var_callindex with offset of var_stack to stack localfget

Opexplicit

  • Operations can be used by users
operation name code description construction
scope 31 pop the top element in stack and push it to variable stack scope
get 32 push the value from variable stack of the value popped the top element in stack
func 33 push the function pc value to stack func 0xHHHHHHHH 0xHH 0xHH[] sweepn jump
apply 34 modify pc to the popped value from stack apply
print 35 console log the popped value from stack print
add 36 pop 2 elements from stack and push the addition of them to stack add
sub 37 pop 2 elements from stack and push the substraction of them to stack sub
div 38 pop 2 elements from stack and push the division of them to stack div
mul 39 pop 2 elements from stack and push the multiplication of them to stack mul
mod 40 pop 2 elements from stack and push the modulo result of them to stack mod
envGet 41 get value from env with popped value from stack as key envGet
envSet 42 set value in env with popped value from stack as key envSet
ifElse 43 detect if the popped value from stack is 1 or 0 ifElse
eq 44 push the equalization of popped 2 values from stack(true is 1 and false is 0) eq
gt 45 greater than detection for 2 popped values from stack gt
ge 46 greater than or equal to detection for 2 popped values from stack ge
lt 47 less than detection for 2 popped values from stack lt
le 48 less than or equal to detection for 2 popped values from stack le
list 49 construct list of data list
index 50 get value from list with index and push to stack index
pop 51 pop the last element from list and push to stack pop
push 52 push the value popped from stack to list push
shift 53 shift the first element from list and push to stack shift
unshift 54 unshift the value popped from stack to list from behind unshift
ANY CANVAS CONTEXT PROPERTY - get or set the canvas context property -
ANY CANVAS CONTEXT OPERATION - run the canvas context methods -